Switch manufacture



April 1959 o. M. HOVGAARD ETAL 2,882,648

SWITCH MANUFACTURE Filed Nov. 1, 1954 SSheejs-Sheet 1 SOURC E OF GAS N.l/VSLEV WVENTORS: 0. M. HOVGAARD O.- M. HOVGAARD ETAI.

April 21, 1959 SWI-TCH MANUFACTURE 3 -Sheets-Sheet Filed Nov, 1. 1954 II I I I 1/ QM HOl GAARD /Nl/ENTORS N. INSLEV ATTORNEY Un e tate Pa fri'0 SWITCH MANUFACTURE Ole M. Hovgaard, Berkeley Heights Township, UnionCounty, N.J., and Norman Insley, Nanuet, N.Y., assignors to BellTelephone Laboratories, Incorporated, New York, N.Y., a corporation ofNew York Application November 1, 1954, Serial No. 465,818

1 Claim. (CL 49-81) pair of essentially parallel flexible reedsoverlapping on one end and whose opposite ends are fixedly retained bythe'corresponding opposite ends of an enclosingvessel. The overlappingends of the reeds or elements are formed as cooperating contactsurfaces, and the enclosing vessel ordinarily is hermetically sealedunder vacuum or a protective gas is injected therein to preventoxidation and/ or other deterioration of the contact surfaces.

. The air gap between the cooperating contact surfaces must bedetermined'accurately if a switch is to function properly upon theapplication of a preselected magnetic field. And, of course, thisrequirement is further emphasized by the need of obtaining the sameoperating characteristics within close tolerances for a group of suchswitches.

.Heretofore, switches of this type have been fabricated in a number ofways, but none of these has proven entirely satisfactory. Priortechniques have entailed, inter alia, fabricating such sealed reedswitches in evacuated Bell jars to obtain a vacuum seal or jars filledwith a gas to obtain a gas atmosphere, using one solid reed and onetubular reed with the evacuation or filling being attained through theagency of the tubular reed which is thereafter sealed, or using twotubular reeds and evacuating the vessel or flushing the gas through thevessel via the reeds and flattening them to seal the switch. These andother methods employed in the past have involved a complexity ofmanipulations, a multiplicity of operations and/or discontinuities inmanufacturing steps, and hence, have not been readily adaptable to massproduction techniques.

One general object of this invention is to improve methods ofmanufacturing switches of the sealed reed type;

More specifically, objects of this invention are to reduce thecomplexity and multiplicity of operations required in the manufacture ofdry reed switches, to expedite the fabrication of sealed reed switcheshaving prescribed and uniform characteristics, and to realize continuityin the series ofsteps in the manufacture of such devices. The attainmentof these objects permits rapid and economical manufacture of sealed reedswitches in large quantities. e a

'In one illustrative embodiment of this invention, the magnetic elementsor reeds are mounted within a vitreous open-ended tube, in the generallydesired parallel and over-lapping relation to one another. The tubeends'are sealed to the elements or reeds at.successive times and a gasfilling is provided in the vessel thus formed.

In accordance with one feature of this invention, with the vessel andmagnetic elementsheld in proper spatial relationship to one another, aflow of the gas to be sealed therein is established through the tubularvessel past the magnetic elements or reeds. The exhaust and intake tubeends with respect to the flow of gas through the tube are sealed in thatorder to their respective elements by heating the tube ends causing themto collapse upon the elements. During the heating of the tube ends thegas flow through the tube is continued and, as a result, a pressureslightly above atmospheric pressure is attained within the enclosingvessel.

In accordance with another feature of this invention, the heating of theends of the vitreous tube to seal them to the reeds is controlled inaccordance with a certain time cycle whereby the pressure upon the innersealing portions of the vessel, caused by the thermal expansion of thegas, is maintained at a reasonable value. This value is such as not toimpede or prevent the formation of seals of sufl'icient strength toinsure hermetically strong joints.

In accordance with a further feature of the invention, one of the reedsis mounted for controlled movement relative to the other to enable theair gap between contact surfaces to be adjusted.

Yet another feature pertains to a mechanism to adjust this air gapspacing automatically such that closure of the contacts will be obtainedby the application of a prescribed magnetic field. This adjustment ismade in cooperation with the gas filling and sealing operations; hence,the performance characteristics of a completed switch meet preassignedrequirements within close limits without undue loss of motion in theover-all manufacturing' process.

The invention and the above-noted and other features thereof will beunderstood more clearly and fully from the following detaileddescription with reference to the accompanying drawing in which:

- Fig. 1 is a side view ofa sealed magnetic reed switch of the typefabricated in accordance with this invention;

Fig. 2 is a front elevational view of one form of apparatus illustrativeof this invention;

Fig. 3 is a side view of this apparatus;

Fig. 4 is a detail view in section depicting the mounting of the tubeand one of the reeds in the apparatus shown in Figs. 1 and 2;

Fig. 5 is a sectional view taken along the lines 5-5 of Fig. 2; and

Fig. 6 is a diagram representing the circuit for controlling theadjustment of the spacingof the reeds and for heating the ends of thevitreous tube to produce the seals between the tube and the reeds.

Referring now to the drawing, the switching device depicted in Fig. 1comprises an elongated vitreous vessel 10 having sealed at opposite endsthereof each of a pair of magnetic reeds 11 and 12. Each of these reedscomprises a flattened flexible portion 13, a circular intermediateportion 14 and a flattened terminal portion 15 as shown in Fig. 1. Theinner ends of the two reeds are in overlapping spaced relation to oneanother and their cooperating surfaces are coated or have thereon alayer of a low-resistance, long-life contact metal. In one particularand illustrative construction, the envelope 10 is constructed of glass,the reeds 11 and 12 are composed of approximately equal parts of nickeland iron, the juxtaposed contact surfaces are gold infused, and thevessel 10 is filled with a protective gas composed of 97 percentnitrogen and 3 percent hydrogen (forming gas).

The apparatus for fabricating switches of the construction shown in Fig.1 comprises, as shown in Figs. 2 to 5, a

base 16' having an upstanding support bracket 17 mounted thereon. Thisbracket 17 acts as a vertical guide way for adjustable carriage 18 whichis slidably supported 7 upon it and may be locked to the bracket 17' bya thumb screw 19. The carriage 18 fixedly retains a chuck 20 forreceiving one of the reeds, for example 12, which may be firmly lockedin place by a thumb screw 21.

A second carriage 26 is slidably mounted upon guide bracket 17 and maybe locked in position through the agency of a thumb screw 33. A secondchuck 27 is fixed ly retained by a third carriage 28 which, in turn, isslidably supported by horizontal rails 29 (Fig. 3) affixed to the secondcarriage 26. Chuck 27 is for receiving the other of the reeds, forexample 11. In the instant apparatus the reed is securely locked in thechuck 27 through manipulation of a thumb screw 32, as illustrated mostclearly in Fig. 4, after its contacting surface is disposed parallel tothe contacting surface of reed 12. The horizontal carriage 28 may bemoved laterally (to the left or right on Fig. 2) through rotation of aworm gear 30 cooperating with a gear segment 31 attached to carriage 28.

Quite often the chuck 27 is constructed so that reed 11 is fixed insofaras its vertical movement is concerned, but left free to turn about itslongitudinal axis. This allows reed 11 to cam its contact surface into aposition parallel to the contact surface of reed 12 when the two reedscome together, thus making a manual adjustment for the same purposeunnecessary. Of course, the result in either case is the same.

As illustrated clearly in Fig. 4, the lower chuck 27 (Figs. 2 and 3) isprovided with a port or aperture 34 whereby a flow of the gas which willform the internal atmosphere for the magnetic elements in the completedswitch may be introduced into the vessel. This port 34 is coupled by anappropriate pipe 35 through a suitable valve 37 to a gas source 36 (Fig.2).

Also supported by the bracket 17 is a mounting block 22 (Fig. whichcarries an arm 23 having therein a V-shaped slot or groove 24 foraccommodating and locating a length of vitreous tubing 10. The tubing isheld firmly in the slot or groove 24 by a flat spring 25.

An electromagnet comprising a coil 38 and pole-pieces 39 is fixedlymounted upon the upstanding bracket 17. Also included in the apparatusand supported at the terminal posts 42 and 43 mounted on the upstandingbracket 17 are a pair of heating coils 40 and 41. These heating coilssurround upper and lower ends (per Fig. 2) of the vessel wherein arepositioned reeds 12 and 11, respectively.

In the fabrication of the switch, a length of vitreous tube 10 is seatedupon the upper surface 27A of the lower chuck 27 and the reeds 11 and 12are locked in their respective chucks 27 and 20, the reeds beingpositioned so that the contact-carrying ends are in preselectedoverlapping spaced relation to one another. The spacing between thecontact surfaces of reeds 11 and 12, that is to say the air gap, shouldbe somewhat greater than that specified for the completed switch. A flowof gas is introduced into and through the tube from the source 36, theflow being lengthwise of the tube and over the two reeds 11 and 12whereby contaminants and atmospheric air within the tube are expelled toprevent deleterious oxidation of the reeds during the sealing steps.With the flow of gas extant, the coil 38 is energized to subject thereeds to a magnetic field of a preselected strength in a manner to bedescribed in detail hereinafter. Through manipulation of the worm gear30, the reed 11 is moved toward the reed 12 until, under the influenceof the mag, netic field, the two reeds contact. As soon as this occurs,the energizing current for the coil 38 is cut ofi and the lowerhorizontally displaceable chuck 27 is firmly locked into position bymanipulation of the thumb screw 33.

With the flow of gas continuing, the heating coils 40 and 41 areenergized sequentially and in that order whereby the respective ends(upper and lower in Fig. 2) of the vitreous tube 10 are rendered plasticsequentially and in that order. As these ends of the vessel 10' becomeplastic, they collapse upon their respective reeds and each is sealed totheir respective reeds. More specifically, the coil 40 is energized torender the upper or outlet end ofthe tube 10 plastic whereupon itcollapses and engages the reed 12. At this time in the cycle and whilethe coil 41 is also energized, the rate of flow of gas into the tube isdecreased. The sequential energization of the heating coil 40 isenergized to render the upper or outlet end of the lated so that thepressure of the gas upon the plastic upper portion of the tube 10 is notgreat enough to prevent formation of a satisfactory hermetic sealbetween the upper portion of the vessel 10 and the reed 12. As energy issupplied to the heating coil 41, the lower end of the tube 10 becomesplastic and collapses about the reed 11. When the lower portion of thetubular container 10 engages the reed 11 the energizing current for theheating coil 41 is cut off. Such timing, as will be obvious to thoseskilled in the art, may be done manually or by the proper constructionand orientation of timing element 50 (Fig, 6) as disclosed hereinafter.The magnitude of the pressure obtained within the sealed tube 10 dependsupon the stagger time relation between the energization andde-energization of heating coils 40 and 41. If the seal created by thefirst coil 40 is not allowed to cool for a sutficient period of timeprior to the sealing of the other end of the tube 10, a blowout" willoccur, i.e., the pressure within the vessel due to the thermal expansionof the gas will become so great that it will blowout or rupture thehermetic seals. Hence, it is quite important that the heating cycle be astaggered one.

It may be remarked that initially the flow of gas from the port 34is'through the tube 10. Following the formation of the seal at the upperend of the tube 10 the flow of gas is into the tube at the lower inletand out at the same end of the tube 10 by way of a leakage path betweenthe lower end of the tube 10 and the positioning surface 27A on thelower chuck 27. Thus, throughout the entire sealing process a continuousflushing of the interior of the vessel 10 by gas is maintained.

It is apparent, of course, that the reeds might all extend from one endof the enclosing vessel. Such an arrangement would not materially afiectthe method described supra. It would mean simply that, upon becomingplastic, the upper end of tube 10 would not collapse about a. reed, butwould close the end of the tube in a glassto-glass seal rather than aglass-to-metal seal.

It will be noted that fabrication of the switch is effected as acontinuous process and, thus, the method of the invention is amenable toeconomical mass production techniques. By virtue of the continualflushing of the tube with gas during the adjusting and sealing steps,most contaminants present are removed, the atmospheric air is replacedby a non-oxygen atmosphere, and any salutary eflect the gas atmospheremay have on the reeds as they are heated is realized. Further, due tothe fact that the seal at one end of the container 10 is formed beforethat at the other, through the control of the heating cycle and the gaspressure, strong hermetic seals are provided between the reeds and thevessel. It is also to be noted that as the gas flow continues during thesealing of the second end of the vessel to its associated magneticelement, the pressure and velocity of the gas at the lower end of thetube is such that it prevents ingress of atmospheric air into the tubeas by an aspirator action adjacent the abutting surface 27A of the chuck27 and the vessel 10.

A circuit for energizing-the coils 40 and 41 and elfecting adjustment ofthe space relation of the reeds is illustrated schematically in Fig. 6.As there shown, the electromagnet 38 is energized from a source 45., theenergizing current being controllable by a switch 61 and a variableresistor 46. The worm gear 30 may be driven by a motor through areduction drive 48, the energizing windings ofthe motor beingillustrated at 47. The motors winding 47 may be energized from source 49to turn the shaft of the motor in either direction over an obviouscircuit under the control of switch 56. The heating coils 4'0 and 41also are arranged for energization from the source 49 over a rotatabletiming element 50 driven by a motor 51. Switch 57 completes the circuitfor motor 51. Associated with the reeds 11 and 12 is a relay 52 havingmake contacts 53 and an armature 54 and energizable from a source 55over an obvious series circuit including the two reeds and switch 62.

In operation, with the coil 38 energized from the source 45, the motor47 is rendered operative by closure of the switch 56, whereby the reed11 is moved toward the reed 12. When, due to the magnetic field set upby the coil 38 and the pole-pieces 39, the reeds 11 and 12 are flexed tocontact each other, the energizing circuit for the relay 52 is completedwhereby the armature 54 bridges the make contacts 53, effectivelyshort-circuiting the windings 47. Thus, lateral movement of the reed 11is stopped substantially instantly upon contact between the two reeds.With the proper positioning of reeds 11 and 12 and gas flowing throughthe vessel via port 34, closure of switch 57 energizes the motor 51 tobegin rotation of the timer 50 whereby the heating coil 40 is energizedand at a specified time thereafter energizing current is supplied to theheating coil 41. As shown, the timer comprises an arcuate conductiveelement 58 of substantially 270 degrees, with which brushes 59 and 60cooperate, each of said brushes being associated with a respective oneof the coils 40 and 41. It should be evident that energizing current issupplied to the heating coil 40 at a prescribed time before current issupplied to the heating coil 41 and, conversely, the supply circuit forthe coil 40 is interrupted at a definite time prior to a similarinterruption for the coil 41.

It is apparent that a ganged switch including switch 61 for energizingcoil 38, switch 56 for energizing motor windings 47, and switch 62 forconditioning the circuit path of relay 52 could be utilized. This gangedswitch might also include a switch for opening the valve 37 (Fig. 2) inorder to fiow gas through the vessel and past the magnetic elements.Further, motor 51 and its associated timing element 50 could be madeoperable in response to the operation of the relay 52 instead of beingcontrolled only by switch 57, as shown by example. And lastly, timingelement in addition to energizing and de-energizing heating coils 40 and41, could enable a solenoid (not shown) whereby the valve 37 (Fig. 2)would be partially closed to reduce the rate of gas flow into the vesselafter the upper end of the vessel has been sealed. With these obviousmodified arrangements, the sequence of operations could be made largelyautomatic.

It is to be understood that the above-described arrangements areillustrative of the application of the principles of the invention.Numerous other arrangements may be devised by those skilled in the artwithout departing from the spirit and scope of the invention.

What is claimed is:

A method of fabricating a dry reed switch of the type having a pair ofelectrodes sealed in a tubular envelope comprising the steps of fixedlymounting said envelope, supporting by one end each of the pair ofelectrodes within the envelope such that each electrode projects inwardly from a diiferent end of the envelope and the free ends of the twoelectrodes overlap, supplying a forming gas to one end of the envelopefor flow past the free ends of the electrodes, while maintaining suchflow heating first the other end of the envelope for causing itscollapse around the supported end of the corresponding electrode and sosealing such end of the envelope, thereafter reducing the rate of flowof the forming gas into said one end of the envelope, and whilemaintaining said flow at a reduced rate heating the said one end of theenvelope for causing its collapse and sealing such end.

References Cited in the file of this patent UNITED STATES PATENTS2,215,641 Freeman Sept. 24, 1940 2,273,437 Dunn Feb. 17, 1942 2,273,439Freeman Feb. 17, 1942 2,508,018 Ellwood May 16, 1950 2,523,903 EllwoodSept. 26, 1950 2,648,167 Ellwood Aug. 11, 1953 2,663,120 Herzog Dec. 22,1953

